| Abstract/Description or Keywords |
Hill Creek Spawning Channel (HCSC) was built as partial compensation for fish losses as a result of the construction and development of hydro-electric dams on the upper Columbia River. The HCSC provides enhanced spawning habitat with controlled flow and substrate to increase survival rates for kokanee (Oncorhynchus nerka), a keystone species within Arrow Lakes Reservoir (ALR). The channel also provides important spawning and rearing habitat for adfluvial rainbow trout (Oncorhynchus mykiss). HCSC is considered a major kokanee producer which supports >30% of all kokanee spawners for Arrow Lakes Reservoir thus contributing to restoring kokanee abundance to pre-impoundment levels. In total, 122,447 kokanee spawners (natural stream + channel) were estimated to have returned to Hill Creek in 2006. From this total, 92,567 kokanee were passed into the spawning channel while 29,880 kokanee utilized the natural stream below HCSC. Mean size of spawners increased in 2006 (26.0 cm fork length) compared to 2005 (21.3 cm). As well, mean fecundity of 240 eggs per female in 2006 was higher compared to that of 214 eggs per female in 2005. Total egg deposition for the combined spawning channel and the natural stream was estimated to be 14,097,672 eggs in 2006 of which 10,604,700 were deposited in HCSC. The estimate in 2006 was considerably lower than the estimate of 19,970,138 eggs in 2005, but relatively close to the design target of 12,250,000 (Lindsay 1982). In summary, 2006 kokanee escapement to HCSC was lower than 2004 and 2005. Production difficulties experienced in 2004 and 2005 have been improved in 2006, evidenced by the high egg-to-fry survival rate, due to an increase in monitoring and maintenance. Improvement to the in-lake carrying capacity, due to nutrient addition, may result in increased future kokanee escapements to HCSC and ALR. Hill Creek Spawning Channel, Arrow Lakes Reservoir, kokanee, adult enumeration, escapement, production, cohort. |
